A plate stacking type heat exchanger is an apparatus that exchanges heat between a high temperature fluid (oil and EGR gas, for example) and a low temperature fluid (water, for example) via stacked plates. The apparatus includes end plates and a plurality of pairs of core plates stacked therebetween, and peripheral flanges of each of the pairs of core plates are bonded to each other in a brazing process, whereby high temperature fluid compartments through which the high temperature fluid flows and low temperature fluid compartments through which the low temperature fluid flows are defined in the space surrounded by the end plates and the core plates, and the high and low temperature fluid compartments communicate with respective pairs of circulation holes provided in one of the end plates. For example, national Publication of International Patent Application No. 2004-530092 describes a plate stacking type heat exchanger of this type.
In a conventional plate stacking type heat exchanger of this type, each of the core plates is provided by forming a substantially flat plate and has a pair of an inlet port for high temperature fluid and an outlet port for high temperature fluid, which communicate with one of the pairs of circulation holes, on both ends in the width direction of the plate on one end side in the longitudinal direction thereof. Further, protrusions are formed on one side of each of the plates. The protrusions extend from the inlet port for high temperature fluid toward the other end side of the plate in the longitudinal direction thereof, form a U-turn region on the other end side in the longitudinal direction of the plate, and return to the outlet port for high temperature fluid. Further, each of the core plates has a pair of an inlet port for low temperature fluid and an outlet port for low temperature fluid, which communicate with the other pair of circulation holes, on both ends in the longitudinal direction of the plate.
That is, in the conventional plate stacking type heat exchanger, the inlet port for low temperature fluid is provided outside the area where the U-turn region is formed on the other end side in the longitudinal direction of the plate, whereas the outlet port for low temperature fluid is provided outside the area where the pair of the inlet port for high temperature fluid and the outlet port for high temperature fluid are provided on the one end side in the longitudinal direction of the plate. Each of the pairs of core plates is assembled in such a way that the side of one of the two core plates that is opposite the one side on which the protrusions are formed faces the side of the other one of the two core plates that is opposite the one side and the protrusions formed on the respective core plates are paired but oriented in opposite directions to form the corresponding high temperature fluid compartment, and the low temperature fluid compartments are formed between the pairs of core plates and between each of the end plates and the core plate adjacent thereto.